The present invention relates to a process for producing aromatic polyketone.
It has been known that aromatic polyketone is excellent in thermal resistance, mechanical properties, electric properties and dimensional stability, is low in water absorption and accordingly, is a remarkably favorable polymer. Although as a process for producing aromatic polyketone, a process comprising reacting 4-phenoxybenzoyl chloride in the presence of boron trifluoride in hydrogen fluoride as a solvent and a process comprising reacting bis-(4-fluoro)benzophenone and bis-(4-hydroxy)benzophenone in the presence of potassium carbonate in diphenylsulfone as a solvent have been known, both processes have many difficulties that (1) both processes necessitate a very expensive monomer, (2) it is necessary to carry out the reaction at a very high temperature of 360.degree. C. and to use a solvent of a relatively high melting point, diphenylsulfone, and (3) impurities are apt to remain in the thus obtained polymer, etc.
On the other hand, in the case of the polymerization by reacting diphenyl ether with phosgene, as is seen in Example 9 of British Pat. No. 1,164,817, the yield of aromatic polyketone is as low as 15% and the inherent viscosity (.eta. inh) is as low as 0.13 dl/g, and accordingly the reaction only gives oligomers.
In addition, a process of reacting diphenyl ether with phosgene or an acid chloride in the presence of aluminum chloride or a Lewis' base has been also proposed (refer to WO No. 84/03892), however, at least in the case of using phosgene as the reactant, it is difficult to obtain the objective polymer of a sufficiently high degree of polymerization. Further, in the case of using aluminum chloride as the catalyst in such a process, it is difficult to completely remove such aluminum chloride from the product.
As a result of the present inventors' studies concerning a process for producing aromatic polyketone while overcoming the above-mentioned difficulties, the present inventors have found a process for producing aromatic polyketone of a high degree of polymerization at a remarkably low cost while using easily removable boron trifluoride instead of using aluminum chloride which is difficultly removable from the product or not using any catalyst, and based on the finding, the present invention has been attained.
The object of the present invention is to provide a process for producing aromatic polyketone while overcoming the above-mentioned difficulties.